Maybe I've watched one too many episodes of Firefly, but I really like the idea of terraforming as an option for human survival on other planets.

I don't, however, think there would be any point in terraforming the Moon or Mars for any purpose other than as an experiment/trial run. As I understand it, part of the reason Earth is habitable is because its core is still mostly molten metal, which keeps the planet warm enough to live on, as well as helping hold the atmosphere together, keeping radiation at bay, and so on. Mars used to be like that, but cooled down faster because it's so much farther away from the Sun; the Moon was as well, but cooled down really fast because it's so small. So I think those two are pretty much "dead," and terraforming efforts might not last very long. But it might have a better shot if the planet(s) we did it to were likely to be able to take on Earth-like conditions and sustain them.

The main problem with the moon, as I understand it, is that it's too light to keep an atmosphere. So, to terraform it, we'll have to continuously replenish the atmosphere to keep it liveable. Of course, we continuously replenish the ISS as well, and if we have the large-scale technology to terraform things then we can use it to keep them terraformed as well.

Another problem, on both the moon and Mars, is the temperature. If it's so cold that the atmosphere freezes out onto the surface, then you can add all the volatiles you want, but you're just going to create more snow. So we'd need lots of powerful greenhouse gases to keep the Sun's energy in. The problem with that is that such an atmosphere wouldn't be very healthy.

Perhaps terraforming can only be a half-way step, with the other half of living on other worlds being adapting ourselves to the circumstances? Perhaps we can change ourselves genetically to be able to deal with higher CO2 concentrations for example. What would the ideal mix be of terraforming the environs and space-hardening ourselves?

_________________Say, can you feel the thunder in the air? Just like the moment ’fore it hits – then it’s everywhereWhat is this spell we’re under, do you care? The might to rise above it is now within your sphereMachinae Supremacy – Sid Icarus

The biggest problem to my mind is bone decalcification due to lower gravity, that's something you either need serious genetic engineering or artifical gravity to overcome. Which means our two options are Venus, in the upper atmosphere, or spinning asteroid habitations.

Do we really need a full 1G to avoid that though? Or would the 1/3 G of Mars be enough? And if you're going to live on Mars anyway, would it be that bad to have bones that are only strong enough for Martian circumstances? Okay, you'll have difficulty visiting Earth, but there are plenty of people here who never visit another continent and still are happy enough.

_________________Say, can you feel the thunder in the air? Just like the moment ’fore it hits – then it’s everywhereWhat is this spell we’re under, do you care? The might to rise above it is now within your sphereMachinae Supremacy – Sid Icarus

Do we really need a full 1G to avoid that though? Or would the 1/3 G of Mars be enough?

I'd guesstimate about three to five years, since it takes about a year for severe decalcification in 0g. We won't know until we get there I guess, but since bone weakening is basically down to the absence of pressure from gravity, about three years is probably accurate.

Lourens wrote:

Okay, you'll have difficulty visiting Earth

You'll have difficulty opening doors without your fingerbones breaking, would be the main problem.

You're just making stuff up, even Nasa's doctors don't know or agree what would happen to a person in long-term 1/3 or 1/6 gee.

I'm not saying I'm not speculating, but logically the best case I can see is maybe two thirds of the bone, mineral, and cardiovascular degradation of zero g. Which is still lethal. Life hasn't evolved on these worlds for a reason.

On the plus side, by the time we have realistically developed the technology for effective terraforming, we should have handily cracked the genetic code to resist these effects. Artificial gravity on the other hand may never be achieved.

Besides, once you fix the acid rain and so on on Venus, it's perfectly suitable as a habitat gravitationally.

Mars has, at best, 10 millibars of pressure. Earth's single bar of pressure is equal to 1000 millibars. The Armstrong Limit which defines the extreme atmospheric-pressure parameters under which humans can survive is 61.2 millibars.

Martian Colonists will therefore require pressure suits or pressurized environments in order to do the exploring, farming, mining, fuel utilization and adventuring during the first five, or so, generations of Martian settlers.

Outgassing of Carbon Dioxide and/ or water ice will help to establish a thicker atmosphere, which, in turn, will help to warm up the planet. Warmer conditions and increased pressure will allow humans to begin actively shaping the planet by forming the land, creating irrigation systems, starting bacteria cultures, etc. Living organisms on the surface of the planet will, in turn, convert Carbon Dioxide into Oxygen which will make the air more breathable for heartier plant species which will repeat the cycle and generate even more oxygen.

Different models for how to outgas Mars' subsurface CO2 and H2O have been studied.

_________________Free societies are the exception in human history--aside from isolated pockets, they have only existed during the four centuries of frontier expansion of the West. Robert Zubrin

As I understand it, part of the reason Earth is habitable is because its core is still mostly molten metal, which keeps the planet warm enough to live on, as well as helping hold the atmosphere together, keeping radiation at bay, and so on. Mars used to be like that, but cooled down faster because it's so much farther away from the Sun; the Moon was as well, but cooled down really fast because it's so small.

First may I address two underlying issues here, perhaps unrelated, but I'd like to quickly correct them regardless.

The molten metallic core of Earth provides the magnetic field which protects the surface of our planet from radiation from the sun. It does not hold the atmosphere together; the ability of a planet to hold an atmosphere is related to its mass. A more massive planet will, generally speaking, have a more voluminous atmosphere. Example for: Jupiter, due to its large mass, collected more gas from the protoplanetary disk during formation than the other planets.

Earth is within the habitable zone of the sun, that is, the range within which liquid water can exist on the surface.It also had enough greenhouse gases in its atmosphere to maintain a relatively warm average temperature. Water and energy and the necessary molecules are what is necessary for life to start.

Nextly, Mars and the Moon both cooled down faster because of their small size. You see, the moon, even though it is closer to the sun, likely cooled down faster than Mars because it is much smaller.

Mars has remnant magnetic fields, predominantly in the southern hemisphere, and that is all because its core no longer produces a substantial magnetic field itself. Remnant fields are carried by ferromagnetic materials after an external field has been applied to them.

That aside, on to TERRAFORMING.

Terraforming involves the conversion of the surface of a planet into an Earthlike environment.

Personally, it’s a romantic ideal but is likely not a physically or economically feasible way of creating a habitat on another planet, regardless of the level of technology.

Here is what would be required:

-For the planet to be capable of holding an atmosphere of the required density for humans to survive, and thick enough to slow or disintegrate space debris a reasonable amount so that infrastructure isn’t destroyed every time there is a meteor shower.

-The planet must have a magnetic field so that people on the surface aren’t being bombarded by solar radiation

-The planet must have enough oxygen in its atmosphere to allow for easy breathing by humans, there must be no toxic chemicals in harmful amounts in the atmosphere, and there must be enough greenhouse gases to allow for a relatively stable temperature to be maintained.

-The average temperature post-terraforming (likely even before) must be above the freezing point of water

The next important thing is the timescale of terraforming; thousands upon thousands of years. You are talking about converting an entire planet into a habitable system, and pumping gas from one place to another is not feasible.

Here is an idea of the volume of the atmosphere on Mars (maths time guys!)

That’s about how much volume you need to fill with gas at the required density. I could tell you how many molecules per square kilometre that should be (I will if you want, but I can’t be bothered to do the math right now).

The point is, it’s huge. And for an atmosphere that is primarily carbon dioxide like Mars, you want oxygen there too. The way that happened on Earth was during the great oxidation event where we had lots and lots of cyanobacteria which are anaerobic. They processed the CO2 into O2 and waste.Took a long time, too.

From what I know, and what I have read, the conclusions that I can formulate lean towards the unfeasibility of terraforming.Now, there are still ways we could create an environment that humans could live in. Biodomes are entirely possible, and indeed could have the highest potential for forming a habitat for humans (not to mention plants and stuff!).The only issue with these would be the gravity of the planet on which you are living which results in the degradation of your organic systems. I’m sure we’ll solve this problem. (:

Please, if I haven’t been clear about anything I have said, ask and I’ll explain further.And no apologies for the long post ;P~R

_________________"Don't tell me that man doesn't belong out there. Man belongs wherever he wants to go--and he'll do plenty well when he gets there."Wernher von Braun, Time magazine, 1958

What about radiation shielding for those biodomes? Can we block out highly energetic radiation while letting in what our ecosystem needs to survive? Polyethylene is good for alpha- and beta radiation protection, but also transparent to visible light. What about gamma and X-rays though?

_________________Say, can you feel the thunder in the air? Just like the moment ’fore it hits – then it’s everywhereWhat is this spell we’re under, do you care? The might to rise above it is now within your sphereMachinae Supremacy – Sid Icarus

What about radiation shielding for those biodomes? Can we block out highly energetic radiation while letting in what our ecosystem needs to survive? Polyethylene is good for alpha- and beta radiation protection, but also transparent to visible light. What about gamma and X-rays though?

Hmm, high energy radiation is always an issue, but the development of shielding technologies is more viable than terraforming an entire planet.Hummmmmmmm! Well, Earth is protected from cosmic radiation by it's magnetosphere. You could potentially emulate such protection by using plasma shielding. If a biodome was made of hexagonal transparent plates held together in an alloy frame [of iron (in steel form) with some heavy atoms in the metallic lattice to aid in absorption of radiation], you could have, at regular intervals, generators that could hold up the plasma shield. http://prl.aps.org/abstract/PRL/v86/i23/p5278_1 maybe

There would probably need to be artificial lighting inside the biodome, Mars, for instance, is a reasonable distance from the sun so plants may need an extra source of light for intensive growth.

Also, because of the lack of tectonic activity on Mars, you could use nuclear reactors (placed a safe distance from colonies) as a very good, long lasting energy source. And not have to worry about earthquakes busting protected waste tanks.

I think the biggest issue with living on a place like Mars is the bone and muscle degradation. Yep.

_________________"Don't tell me that man doesn't belong out there. Man belongs wherever he wants to go--and he'll do plenty well when he gets there."Wernher von Braun, Time magazine, 1958

Earth is protected from cosmic radiation by it's magnetosphere. You could potentially emulate such protection by using plasma shielding. If a biodome was made of hexagonal transparent plates held together in an alloy frame [of iron (in steel form) with some heavy atoms in the metallic lattice to aid in absorption of radiation], you could have, at regular intervals, generators that could hold up the plasma shield.

I think the biggest issue with living on a place like Mars is the bone and muscle degradation. Yep.

The plasma shield idea might work, but would have to be superhumanly reliable. One failure would leave the crews to be fried before they can get it back up, and even a momentary blink could cause cancers to crop up years later. It might be nice, and light for a temporary defense while hard ones are built, but eventually, you'll want a more permanent solution.

Degeneration wouldn't be that bad a about a third the gravity we're used to. If it's a 1 way ticket, I believe we'd simply adapt, but have trouble coming back to Earth afterwards. An orbital centerfuge could be used to recondition people returning from Mars much like decompression chambers for divers. Slowly spin up over a period of months, and your body would rebuild hardy enough to reaclimate.

_________________"You can't have everything, where would you put it?" -Steven Wright.

...One failure would leave the crews to be fried before they can get it back up, and even a momentary blink could cause cancers to crop up years later. ...

Degeneration wouldn't be that bad a about a third the gravity we're used to. If it's a 1 way ticket, I believe we'd simply adapt, but have trouble coming back to Earth afterwards. An orbital centerfuge could be used to recondition people returning from Mars much like decompression chambers for divers. Slowly spin up over a period of months, and your body would rebuild hardy enough to reaclimate.

I think on Mars, being suddenly fried would be an issue, but not that huge. Plasma shielding could quite easily be a permanent solution. But yes, looking for others would also be a good idea. I'll get back to you if I ever get anywhere in the field of plasma physics (:

Unfortunately, there is no chance of re-acclimatising a bone and muscle degenerated person. I do believe it is permanent. At least on the scale of 1/3 gravity would be. If they went to Mars to stay on Mars, then no, it's not an issue. Returning will always be a factor unless we can find an artificial way of preventing, decelerating or correcting that level of degradation.Of course, when I get home I should have a look into this.arXiv.org is an excellent place to look up papers on anything, so if you feel like looking up anything at all (or anyone), there is a great place to start.Please take anything I say on biological matters with a grain of salt, I only have first year university bio (I'm adv. physics major in third year), and I'll have to verify anything here.

Poke and prod me via PM if I don't get back to this

_________________"Don't tell me that man doesn't belong out there. Man belongs wherever he wants to go--and he'll do plenty well when he gets there."Wernher von Braun, Time magazine, 1958